Understanding Client Access

The Client Access server role is one of five distinct server roles for Microsoft Exchange Server 2010. It supports the Outlook Web App and Microsoft Exchange ActiveSync client applications, and the Post Office Protocol version 3 (POP3) and Internet Message Access Protocol version 4rev1 (IMAP4) protocols. The Client Access server role also provides access to free/busy data by using the Availability service and enables certain clients to download automatic configuration settings from the Autodiscover service.

The Client Access server role accepts connections to your Exchange 2010 server from different clients. Software clients such as Microsoft Outlook Express and Eudora use POP3 or IMAP4 connections to communicate with the Exchange server. Hardware clients, such as mobile phones, use ActiveSync, POP3, or IMAP4 to communicate with the Exchange server. You must install the Client Access server role in every Exchange organization and every Active Directory site that has the Mailbox server role installed.

In addition to needing a Client Access server in every Active Directory site that contains a Mailbox server, it’s important to avoid restrict traffic among Exchange servers. Otherwise, Exchange functionality can be negatively affected. Make sure that all defined ports used by Exchange are open in both directions between all source and destination servers. Installing a firewall between Exchange servers or between an Exchange Server 2010 Mailbox server or Exchange Server 2010 Client Access server and Active Directory isn’t supported. However, you can install a network device as long as traffic isn’t restricted and all available ports are open between the various Exchange servers and Active Directory. For a complete list of Exchange Server 2010 ports, see Exchange Network Port Reference.

Outlook Web App lets you access your e-mail from any Web browser. Outlook Web App (known as Outlook Web Access in earlier versions of Microsoft Exchange) has been redesigned in Exchange 2010. Features such as Chat, Text Messaging, mobile phone integration, and Conversation View provide an enhanced user experience from any computer that has a Web browser. In Exchange Server 2010, these features can be accessed from an expanded set of Web browsers including versions of Internet Explorer later than 6.0, Firefox, Safari, and Google's Chrome.

If you use a phone that has Windows Mobile 5.0 with the Messaging Security and Feature Pack (MSFP) installed or a later version, your mobile phone will support Direct Push. Direct Push technology is built into Exchange ActiveSync and keeps a mobile phone continuously synchronized with an Exchange mailbox.

Note:

Mobile phones and devices that are running versions of Windows Mobile earlier than Windows Mobile 5.0 with MSFP can still send and receive messages on a set schedule, but can't use Direct Push to synchronize items as they arrive. All versions of Windows Mobile and Pocket PC operating systems can synchronize items with Exchange 2010 by using a cable connection to a desktop or portable computer.

For more information about Exchange ActiveSync, see the following topics:

In addition to supporting MAPI and HTTP clients, Exchange 2010 also supports POP3 and IMAP4 clients. By default, POP3 and IMAP4 are installed, but the services are disabled when you install the Client Access server role.

The Exchange 2010 Availability service provides secure, consistent, and up-to-date free/busy data to computers that are running Microsoft Office Outlook 2007 and later versions of Outlook. These versions of Outlook use the Autodiscover service to obtain the URL of the Availability service. Essentially, the Autodiscover service helps capable Outlook clients locate different Web services, such as the Microsoft Exchange Unified Messaging service, the Offline Address Book, and Availability services.

For more information about the Availability service, see the following topics:

The Autodiscover service enables Outlook clients and some mobile phones to receive their necessary profile settings directly from the Exchange server by using the client's domain credentials. These settings automatically update the client with the information that's needed to create the user's profile.

For more information about the Autodiscover service, see the following topics: